Uterus

Uterus

The uterusThe muscular organ where a fertilized egg implants and develops. is a hollow, muscular, pear-shaped organ located in the female pelvis, between the bladderA muscular organ that stores urine before excretion. and the rectumThe final section of the large intestine, where feces are stored before elimination.. It consists of three main regions. The fundusThe dome-shaped upper part of the uterus. is the broad, curved upper portion above the openings of the uterine (fallopian) tubes. The body forms the central portion where implantation typically occurs. The cervix is the narrow lower portion that projects into the vaginaThe muscular canal connecting the uterus to the external genitalia.. The cervix is further divided into the internal os. This marks the opening between the uterine cavity and the cervical canal. The external os opens into the vaginal canal. Just above the internal os is the isthmusA narrow portion of the uterine tube connecting to the uterus.. It is a slightly narrowed region. This region connects the body of the uterus to the cervix.

Ligaments

The adnexa extend laterally from the uterus. This term refers collectively to the uterine tubesAlso called fallopian tubes, they transport the oocyte to the uterus. (fallopian tubes). It also includes the ovariesThe female gonads that produce eggs and hormones. and supporting ligaments. The broad ligaments support the uterus and house the fallopian tubes, ovaries, blood vessels, and nerves. The round ligaments help maintain the anteverted position of the uterus. The uterosacral ligaments anchor the uterus posteriorly to the sacrumTriangular bone formed by fusion of five vertebrae; connects spine to pelvis..

The mesovariumA fold of the broad ligament that supports the ovary. is a short fold of peritoneumThe membrane lining the abdominal cavity and organs.. It connects the anteriorThe front of the body or toward the front when standing in the anatomical position. surface of the ovary to the posterior layer of the broad ligament of the uterus. It acts as a small mesenteryA fold of peritoneum that supports and connects the intestines to the abdominal wall. for the ovary, providing a pathway for blood vessels, lymphatics, and nerves.

The uterosacral ligaments are paired fibrous bands. They extend from the posterior aspect of the cervix and upper vagina to the anterior surface of the sacrum. They play a crucial role in maintaining the position of the uterus within the pelvic cavityThe body cavity that houses the reproductive organs and bladder. by anchoring it posteriorly. These ligaments are situated lateralAway from the midline of the body. to the rectum. They are medialToward the midline of the body to the ureters. They form the lateral boundaries of the rectouterine and rectovaginal spaces. Structurally, each uterosacral ligament comprises a superficialNear the surface of the body. part made of smooth muscle, connective, and adipose tissue, and a deepAway from the surface of the body. part containing splanchnic nerve fibers and vessels

Tissue Layers

The innermost layer is the endometriumThe inner lining of the uterus that thickens during the menstrual cycle to support a potential pregn, a mucous membrane that undergoes cyclic changes in response to hormonal fluctuations. The endometrium thickens during the menstrual cycleThe monthly cycle of changes in the female reproductive system. to prepare for implantation of a fertilized egg. If pregnancy does not occur, it is shed during menstruation. It has two sub-layers. The functional layerThe superficial layer of the endometrium that is shed during menstruation. is shed each cycle. The basal layerThe deeper layer of the endometrium that remains intact during menstruation and regenerates the func regenerates the functional layer each cycle.

The middle layer is the myometriumThe thick muscular layer of the uterus. It is a thick layer of smooth muscle responsible for uterine contractions during menstruation, labor, and delivery. This layer enables the uterus to expand during pregnancy and contract during childbirth to help push the baby out. The outermost layer is the perimetriumThe outermost layer of the uterus., a thin serous membrane that covers the outer surface of the uterus. It is part of the peritoneum and provides a protective covering.

Endometrium

The basal layer of the uterus is considered the deeper, more stable layer of the endometrium. The basal layer does not shed during menstruation. Instead, it remains intact and serves as the foundation for the regeneration of the functional layer after each menstrual cycle. The basal layer contains stem cellsThe basic structural and functional units of life.. These stem cells enable the renewal of the endometrium. This renewal allows for the cyclical buildup of the functional layer in preparation for potential pregnancy.

The functional layer of the uterus is the innermost part of the endometrium. It thickens in response to hormonal changes during the menstrual cycle. This layer is where the embryo would implant if fertilization occurs. In this diagram, you can see that the arteriesBlood vessels that carry oxygenated blood away from the heart (except pulmonary arteries, which carr and veinsBlood vessels that return deoxygenated blood to the heart (except pulmonary veins, which carry oxyge are growing from the basal layer of the endometrium. They extend up into the functional layer. These arteries have a characteristic appearance of coils, however, the veins do not show this type of structure. As the functional layer grows and builds up pre-ovulation, mucus glands invade the functional layer.  Notice how the coiled arteries are growing up from the basal layer. The mucus glands are extending down from the lumenThe inside space of a hollow organ or structure..  

Endometriosis

Endometriosis is a medical condition. Tissue similar to the endometrium—the lining of the uterus—grows outside the uterus. It most commonly grows on the ovaries, fallopian tubes, and pelvic lining. These displaced tissue patches still respond to hormonal changes during the menstrual cycle. They thicken, break down, and bleed as they would inside the uterus. However, this tissue is outside the uterus and has no way to exit the body. It can cause inflammation, pain, and scar tissue formation. Additionally, it can lead to adhesions between organs.

The symptomsSubjective experiences reported by the patient (e.g., nausea, fatigue). of endometriosis can vary. They often include chronic pelvic pain, especially during menstruation. Painful intercourse and heavy menstrual bleeding are also common. In some cases, infertility may occur. The exact cause of endometriosis is not fully understood, but theories include retrograde menstruation, immune system disorders, and genetic factors. Treatment options may involve pain relief medications, hormone therapy to reduce or stop menstruation, and surgical removal of the endometrial-like tissue in severe cases